| A critical layer thickness (CLT) between strained and relaxed InxGa1-xN films for the InxGa 1-xN/GaN material system for both single and double heterostructures was determined to be approximately 25 nm, 40 nm, and 80 nm for InN compositions of 16%, 10%, and 5%, respectively, primarily by determining the onset of photoluminescent band-edge emission red-shift as a function of InxGa1-x N thickness.;In addition, the optical band gaps as a function of InxGa 1-xN over 0 ≤ x ≤ 0.25 for strained and relaxed films were determined. Band-gaps deduced from optical transmission were in good agreement with the optical band-gaps determined by photoluminescence for very thick relaxed InxGa1-xN films. InxGa 1-xN. The band-gap's dependence on InN mole fraction, x, for strained and relaxed InxGa1-xN films was fit to a parabolic function with strained and relaxed film bowing parameters of 2.1259 eV and 2.7503 eV, respectively, using a relaxed InN band-gap endpoint of 0.77 eV or 3.4159 eV and 4.112 eV, respectively, using a relaxed InN band-gap endpoint of 1.89 eV.;Metal semiconductor metal (MSM) photodetectors were fabricated with back to back Schottky diodes on an InxGa1-xN/GaN structure. Turn-on wavelengths were found to increase between 370 nm and 430 nm by varying the indium mole fraction in the InxGa1-xN active layer from x = 0 to x = 0.13. Schottky contacts became increasingly leaky and dark current increased substantially for InxGa1-x N layers exceeding the CLT which is most likely associated with CLT electronic defects such as surface traps due to rough surfaces and recombination via mid-band-gap traps within the InxGa1-xN layer.;A comparison study on the tensile strained GaP/GaAs compound system, was investigated and the CLT was experimentally determined to be within 100 A and 140 A with a variety of experimental techniques. All the experimental methods used exceeded the CLT value of 16 A predicted by the force balance Matthews Blakeslee model. This indicated that the CLT could be exceeded for growth of films using low temperature two-dimensional (2D) atomic layer epitaxy (ALE) growth. |
